High Efficiency X-ray Fluorescence Detectors

DESCRIPTION (provided by applicant): It has been repeatedly emphasized in various reports and workshops [1-2] that the development of better X- ray fluorescence detector systems is urgently needed to solve the saturation problems with the currently availab le detectors. The multilayer analyzer array detector (MAAD) using linearly graded multilayers has been successfully developed to handle the large photon flux from the third generation synchrotron sources. However, this type of detectors has limited detecti on solid angle restricted by its vertical and horizontal acceptance. The detectors will suffer largely degraded energy resolution and loss of throughput if horizontal acceptance angle is increased. In the Phase I proposal, we have proposed to develop multi layer array analyzer detectors using radially graded multilayers. By largely increasing the horizontal acceptance per multilayer, this new design provides a 2.5 times of collection solid angle increase. Furthermore, the new design substantially reduces the energy resolution and improves the throughput of the analyzers due to the preferred gradient design and optimized deposition material selection. Thus we have demonstrated 6-8 times of combined improvement of performance over the previous analyzer detector design. In a subsequent investigation after the completion of our Phase II project (RR015994), we have demonstrated that large background rejection, in excess of 10,000, can be achieved with a dual multilayer analyzer in plus configuration, rather than minus configuration that we have proposed previously. Thus we will combine the two technologies, namely the radially graded multilayer technology and the new dual multilayer analyzer configuration to fabricate very desirable fluorescence analyzer detecto rs to benefit the user community. In the Phase II project, we will design, fabricate and test one radially graded multilayer array analyzer detector (RMAAD) optimized for energies from 1.2 to 4 KeV, and one dual multilayer array analyzer detector (DMAAD) i n the plus configuration optimized from 3.5 to 10 KeV. We will adopt a modular design for the RMAAD unit, where smaller unit containing 5 miltilayers can be added to form a full-scale unit. The DMAAD unit can work as a RMAAD when large background rejection is not required. The proposed DMAAD will allow for the elemental detection in ppb levels or in Physiologically relevant concentrations. In addition to the improved detection efficiency, the proposed analyzer detectors extend the current fluorescence detec tion capability in two crucial areas: very dilute system regime and intermediate to lower energy regions, which are most relevant to biology. The market of the new detectors will no longer be restricted to synchrotron beamlines with intense flux, but all t he beamlines which are involved in spectroscopy and fluorescence analysis. The advances made in this proposal will enhance the capability of research for x-ray spectroscopy and fluorescence analysis under high count rate achievable at the current and next generation synchrotron sources.